The present invention relates to an optical system for shaping a laser beam and to a laser system having such an optical system.
When incident on an interface, a laser beam is generally split into three parts: a first part is reflected at the interface (reflected laser beam), a second part passes through the interface into the second optical medium (transmitted laser beam) and a third part is absorbed at the interface (absorbed laser beam). An interface is defined as a surface that is arranged between two media of different refractive indices. An interface at which a laser beam predominantly passes from a first into a second optical medium is referred to as a transmitting surface. An interface at which a laser beam is predominantly deflected within an optical medium is referred to as a reflecting surface. The respective fractions of the reflected, transmitted and absorbed laser beam can be modified, for example, via the wavelength and/or the angle of incidence of the incident laser beam and/or via a coating of the interface.
German Patent Document No. DE 10 2010 028 794 discloses an optical system for shaping a laser beam, comprising a first optical element that is designed, at least in some segments thereof, as a base member having a lower base, an upper base parallel to the lower base, and a lateral surface abutting the lower and upper bases. The lateral surface of the base member is designed, at least in some segments thereof, as a transmitting surface for the laser beam. The base member comprises a first cutout portion having a lower base that is arranged in the upper base of the base member, and a lateral surface that is designed, at least in some segments thereof, as a first reflecting surface for the laser beam
An incident laser beam is deflected at the lateral surface of the first cutout portion, which lateral surface forms the first reflecting surface, and reshaped into a ring-shaped laser beam. In order to be able to generate on a target surface a horizontal line-shaped laser mark, it is necessary for the incident laser beam to be deflected through 90°. The known optical system for shaping a laser beam makes it possible to generate a line-shaped laser mark on a target surface without requiring much aligning effort. A shortcoming lies in that the optical system is sensitive to tilting of the first reflecting surface relative to the incident laser beam.
The aim of the present invention is therefore to develop an optical system for shaping a laser beam and a laser system having such an optical system, in which the aligning effort is further reduced and which additionally is insensitive to tilting of the reflecting surface relative to the incident laser beam.
According to the present invention, it is provided that the base member comprises a second cutout portion having a lower base that is arranged in the lower base of the base member, an upper base that is designed at least in some segments thereof as a transmitting surface for the laser beam, and a lateral surface abutting the lower and upper bases, the lateral surface being designed at least in some segments thereof as a second reflecting surface for the at least segmentally ring-shaped laser beam. The angle between the first reflecting surface and the lower base of the first cutout portion, and the angle between the second reflecting surface and the lower base of the second cutout portion are aligned relative to one another in such a way that an incident laser beam is deflected through 90°.
The optical element according to the invention has a first and a second reflecting surface for the laser beam, wherein the lateral surface of the first cutout portion that is arranged in the upper base forms the first reflecting surface and the lateral surface of the second cutout portion that is arranged in the lower base forms the second reflecting surface. Owing to the double reflection of the laser beam, the optical system according to the invention is insensitive to tilting of the first reflecting surface relative to the incident laser beam. The first and the second reflecting surfaces are integrated into the base member of the optical element, such that the alignment of the first and second reflecting surfaces relative to each other takes place during production of the first and second cutout portion in the base member and only one optical mount is required.
In order to generate on a target area a line-shaped laser mark that is closed over 360°, all bounded surfaces in which the directional derivative of the bounding line is continuous may be used as suitable bases for the base member. If the directional derivative is not continuous at any point, the ring-shaped laser beam is interrupted and the line-shaped laser mark on a target surface is therefore not closed over the entire circumference of the mark. In applications in which a closed laser mark is not required, it is possible to use bases in which the directional derivative of the bounding line is discontinuous at one or more points, like in a polygonal base, in which the directional derivative of the bounding line is continuous in the area of the sides and not continuous in the area of the corner points.
In a preferred embodiment, a further optical element is provided that is integrated into the lateral surface of the base member, into the lateral surface of the first cutout portion, into the upper base of the second cutout portion, and/or into the lateral surface of the second cutout portion. The term “integrated” means that no interface exists between the base member and the further optical element. The optical element according to the invention has four interfaces between a first optical medium which is the base member, and a second optical medium which is the surrounding environment. These interfaces are utilized in order to integrate further optical elements into the base member. This embodiment has the advantage that the alignment of the optical elements takes place during manufacturing of the optical system and that only one optical mount is required.
Particularly preferably, the further optical element is designed as a diffractive optical element. Diffractive optical elements split an incident laser beam into different orders of diffraction according to the angle and have the advantage that laser beams can be shaped into nearly any desired beam distribution. A diffractive optical element can be created retroactively in a base member by scanning texturing methods, such as diamond turning, laser- or electron writing. This embodiment has the advantage that the alignment of the optical elements takes place during manufacturing of the optical system and that only one optical mount is required.
In a further preferred embodiment a further optical element is provided that directly abuts the lateral surface of the base member, the lateral surface of the first cutout portion, the upper base of the second cutout portion, and/or the lateral surface of the second cutout portion. The term “directly abutting” means that the base member and the further optical element have a common interface, and no other optical element or medium having a different refractive index, such as for example air, is located between the optical surfaces of the two optical elements. This embodiment has the advantage that it allows two different materials to be combined, and the properties of the optical system can thus be adapted to the given requirements in a more flexible and improved manner. Despite different optical materials, only one optical mount is required and the alignment of the two optical elements takes place during manufacturing, rather than at a later time.
In a preferred embodiment, the at least one further optical element is designed as a beam-shaping optical element that shapes the laser beam in a plane perpendicular to a propagation direction of the laser beam. The laser beam can be shaped, for example, with the aid of collimating optics or focusing optics.
In a further preferred embodiment the at least one further optical element is designed as a beam-shaping optical element that shapes the at least segmentally ring-shaped laser beam in a plane perpendicular to a propagation plane. This embodiment has the advantage that a narrow line-shaped laser mark can be generated on a target surface. The ring-shaped laser beam can be shaped, for example, with the aid of collimating optics or focusing optics.
In a further preferred embodiment the at least one further optical element is designed as a beam-shaping optical element that shapes the at least segmentally ring-shaped laser beam in a plane parallel to a propagation plane of the ring-shaped laser beam. This embodiment has the advantage that spot-shaped laser marks can be generated on a target surface, in addition to a line-shaped laser mark. Diffractive optical elements shape a laser beam in such a way that the zero order of diffraction of the laser beam generates on the target surface a line-shaped laser mark and the higher orders of diffraction, in particular the first order of diffraction, generate spot-shaped laser marks. The spot-shaped laser marks can enclose between them a defined angle and may be used, for example, to transfer angles from one target surface to another target surface. This application expands the spectrum of applications of the optical system according to the invention.
In a preferred embodiment, the first cutout portion of the base member has an upper base that is parallel to the lower base, which upper base is designed at least in some segments thereof as a transmitting surface for the laser beam. This embodiment has the advantage that a spot-shaped plumb beam is generated in addition to the line beam. The beam shape of the plumb beam can be adjusted via an optical element that is integrated into or directly abuts the upper base. A collimated or focused plumb beam can be generated by collimating or focusing optics.
Also proposed is a laser system comprising a beam source for generating a laser beam and comprising the optical system according to the invention. Preferably, an adjustment device is provided whereby the position of the beam source relative to the optical system and/or the position of the optical system relative to the beam source are adjustable in a propagation direction of the laser beam and/or in a plane perpendicular to the propagation direction of the laser beam. The ability to adjust between the beam source and the optical system has the advantage that the opening angle of the ring-shaped laser beam can be adapted to the measuring task at hand and the available intensity of the beam source can be optimally utilized.
In a preferred embodiment of the laser system, a first optical system which generates a first at least segmentally ring-shaped laser beam, and at least one further optical system that generates a further at least segmentally ring-shaped laser beam are provided. Particularly preferred is a third optical system which produces a third at least segmentally ring-shaped laser beam. The ring-shaped laser beams are arranged perpendicular to one another or at a specified angle. In a further preferred embodiment of the laser system, at least one optical system is designed in such a way that a spot-shaped laser beam is generated in addition to an at least segmentally ring-shaped laser beam.
Embodiments of the invention will be described below with reference to the drawings. The drawings are not necessarily intended to show the embodiments true to scale, but instead the drawings are rendered, where expedient for explanation purposes, in schematic and/or slightly distorted form. With regard to teachings readily apparent from the drawings, reference is hereby made to the pertinent prior art for further details. One should bear in mind that a great variety of modifications and changes can be made with respect to the form and detail of an embodiment without departing from the general idea of the invention. The features of the invention that are disclosed in the description, in the drawings and in the claims may be essential for further enhancement of the invention, by themselves and/or in any combination thereof. Furthermore, the scope of the invention also covers any and all combinations of at least two of the features disclosed in the description, in the drawings and/or in the claims. The general idea of the invention is not limited to the exact form or detail of the embodiments shown and described hereinbelow, nor limited to a subject matter that would be limited when compared to the subject matter as claimed in the claims. Where dimensional ranges are given, values that lie within the stated limits shall be usable and claimable also as threshold values. For reasons of simplicity, like reference symbols are used hereinbelow for identical or similar elements or elements of identical or similar function.